Is it a Regression:No
(Jre 8u40b19/32bit on OEL6.4-RedHat-x86,the results:failed as the same issue.)
(Jre8u40b01/32bit on OEL6.4-RedHat-x86,the results: there is no mixedcode dialog shown up.)
(Jre8u33b01/32bit on OEL6.4-RedHat-x86,the results: there is no mixedcode dialog shown up.)
(Jre8u31b01/32bit on OEL6.4-RedHat-x86,the results: there is no mixedcode dialog shown up.)
(Jre8u27b01/32bit on OEL6.4-RedHat-x86,the results: there is no mixedcode dialog shown up.)
(Jre8u26b26/32bit on OEL6.4-RedHat-x86,the results: there is no mixedcode dialog shown up.)

Test result on the last GAed release for this train:Fail(Jre8u33b05/32bit on OEL6.4-RedHat-x86,the results:there is no mixedcode dialog shown up.)

[if Fail] Test result on FCS: Fail(Jre8b132/32bit on OEL6.4-RedHat-x86,the results:the mixedcode dialog is not same as showed in mixedcode.png,refer to JDK-8062380)

Is it a platform specific issue:Not sure
test on win7-x86 with Jre8u40b20/32bit,the results:Pass
test on mac10.9 with Jre8u40b20/64bit,the results:Pass
Exception/Error from Log:
http://scaaa008.us.oracle.com:9502/runs%2F676947.ManualSubmit-1/mixedcodeJWScenarios/testMixedCodeDialogContent.jtr
Copy JDF workspace,install test jre,and run this case
Steps to reproduce:
1.The option "Enable - show warning if needed" is selected by default. Run this test with the default settings i.e. Enable - show warning if needed.
2.Clear cache: javaws -uninstall
3.For JDK7u51 or higher or JDK8, add test URL prefix "http://localhost:8080/mixedcodeJW/" to JCP->Security->Exception Site List to avoid blocking
4.Load following app from CMD: javaws http://localhost:8080/mixedcodeJW/jnlp/testPubNameMixedCodeSignedToUnsigned.jnlp
5.Make sure two security pop-ups are there for both Signed and unsigned applets
6.Accept these warnings.
7.Make sure the third pop-up for mixed warning dialog is there, make sure it has native windows look and feel. The dialog should have focus on it and be modal.
8.In mixedcode dialog check if application name on mixed code dialog is with expected value: Publisher. The other content in dialog should be same as showed in mixedcode.png in test scenarios directory
9.Click on "more informaiton", the follow up dialog should be the same as showed in mixedcode.png in test scenarios directory

The actual result:
The text location of "More information" overlap with "code" in mixed code dialog
Please refer to attachment.jpg